Method for the manufacture of batteries

ABSTRACT

A method of encasing batteries where the battery electrodes are assembled with spacers maintaining the electrodes in a spaced relationship to define an electrolyte cavity. In practicing the method, the electrode assembly is immersed in a body of molten casing material whereby the casing material solidifies to form a web between the electrodes and define the electrolyte cavities. The supports for the assembly during immersion extend across the electrodes and are coated with casing material so that upon removal of the supports transverse tubular manifolds are defined. A single port to the manifold and the plurality of electrolyte cavities is also provided upon removal of the supports.

United States Patent Jones [451 Apr. 11, 1972 [54] METHOD FOR THEMANUFACTURE 3,120,572 2/1964 Shannon....; ..264/277 x OF BATTERES3,196,049 7/1965 Schilke l ..l3 [72] Inventor: Kenneth R. Jones, Mequon,Wis. 3'l85592 5/1965 Klrk et a 6/l00 [73] Assignee: Globe-Union Inc.,Milwaukee, Wis. P imary Examiner-Anthony Skapars Filed g 16 1968Attorney-Pendleton, Neuman, Williams & Anderson [21] Appl. No.: 777,932[57] ABSTRACT Related US Application Data A method of encasing batterieswhere the battery electrodes are assembled with spacers mamtammg theelectrodes 1n a Dlvlslon of 383,159, 16, 1964, spaced relationship todefine an electrolyte cavity. In practic- 3,431,148- ing the method, theelectrode assembly is immersed in a body of molten casing materialwhereby the casing material solidifies to form a web between theelectrodes and define the elec I? trolyte cavities. The pp for theassembly during immer [5 8] Flew of Search 5 i sion extend across theelectrodes and are coated with casing material so that upon removal ofthe supports transverse tubular manifolds are defined. A single port tothe manifold and [56] References Cited the plurality of v electrolytecavities is also provided upon UNITED STATES PATENTS removal of the pp2,464,029 3/1949 Ehrman ..264/277 X 6 Claims, 5 Drawing Figures METHODFOR THE MANUFACTURE OF BATTERIES This application is a division ofapplication Ser. No. 383,159, filed July 16, 1964, now U.S. Pat. No.3,431,148.

This invention relates to an improved battery construction and to amethod and an apparatus especially useful in the manufacture of saidimproved battery construction. One particular battery to which theteachings of this invention are especially applicable is that disclosedand claimed in a copending application of Jones et al., Ser. No.287,171, filed May 29, 1963, now abandoned and assigned to the sameassignee as the instant application.

The batteries of said copending application will be describedhereinafier as an exemplary form to which the instant invention isapplied. Such batteries employ an anode of magnesium and a cathode ofsilver chloride in a battery cell in which the electrolyte is, forexample, sea water. The cell is activated by immersion of the unit intosea water, provision being made to permit the sea water to enter thecell and to act as an electrolyte, and also to pass through the cell toremove products of the battery action, and, in some cases, to providecontrol of thermal conditions within the battery.

Such deferred action batteries are normally composed of a plurality ofcells, and the cells are customarily separated by means of imperviousbut electrically conducting partitions, each separating the anode of onecell from the cathode of an adjacent cell, electrically connecting theelectrodes of the cells in series, and preventing electrolyte frommigrating between the cells.

In a preferred form of the battery construction, a plurality of cells ofthe type described above are interconnected as an assembled unit andencased in a plastic casing material which is applied to the exterior ofthe assembled unit by dipping the same into a molten supply of thecasing material. As taught in the aforementioned Jones et al.application, the temperature of the assembled battery unit prior todipping is below the setting temperature of the casing material, wherebythe liquid casing material which comes into intimate contact with therelatively cool battery assembly becomes more viscous and forms a thinviscous skin about the battery. This permits the build-up of additionalmaterial to form the casing while preventing contamination of thebattery interstices. The material hardens after withdrawal of the dippedunit to form an integral and homogeneous casing surrounding the batteryunit.

In prior batteries of the deferred action type, a plurality of portswere formed in the casing to provide for ready access of sea water tothe cells when the battery is immersed. It has been found, however, thatthe efiiciency of the prior deferred action batteries and their life isadversely afiected by leakage of electrical current between the cells,occurring in the vicinity of the ports provided in the casing. Onefactor in this leakage phenomena is the fact that the edges of theelectrodes are exposed to a large body of sea water in the vicinity ofthe port, and the sea water therefore forms a relatively largecross-section, low resistance circuit interconnecting the various cellsand electrodes of the battery. The present invention contemplates thereduction of the magnitude of the intercell leakage by providing hoodsover the area in which the electrodes are exposed to the electrolyte,and thereby reducing the cross-sectional area of the path through whichleakage current may pass between the battery cells, and consequentlyraising the leakage resistance.

This arrangement achieves the advantage of reducing intercell leakageand thereby improving the efficiency and lengthening the life of thebattery, and also produces a more desirable flow of electrolyte throughthe cells and consequent improvement in the voltage-time characteristic.

The present invention also provides an improved method of forming acasing for a deferred action battery which has hoods defining manifoldsintegral with the casing and ports of reduced cross-sectional area.

The present invention also provides improved apparatus by which a casingwith such manifolds and ports may be formed.

Accordingly, it is a principal object of the present invention toprovide an improved integral casing for a battery having ports andmanifolds adapted for the ingress and egress of electrolyte from thebattery cells which have a smaller leakage cross-section than thoseheretofore known.

A further object of the present invention is to provide a casing for amultiple cell deferred action battery having passageways interconnectingthe cells of the battery and integral hoods disposed over thepassageways.

Another object of the present invention is to provide a method forforming a battery casing around the assembled components of a deferredaction battery in such a manner as to provide ports for the ingress andegress of electrolyte which have a reduced leakage cross-section andintegral hoods over the passageways.

Another object of the present invention is to provide improved apparatusfor performing the process of the invention.

One advantage which is derived from the practice of the presentinvention is the material improvement in the voltagetime characteristiccurve of the battery for various environments and particularly forconditions in which the electrolyte is maintained at a relatively lowtemperature, a circumstance which prevails when the battery is activatedby cold sea water. This improvement is exemplified by an output voltageunder constant current conditions, exhibiting a gradually rising slopeduring the life of the battery until just prior to exhaustion of thebattery. While an understanding of the underlying theory for thischaracteristic is not essential to a utilization of the principle, it isbelieved that this advantageous voltage characteristic is achievedbecause the reduced cross-sectional area of the electrolyte portsreduces the flow of electrolyte through the ports so that the internaltemperature of the battery rises and the salt content of the electrolyterises as a result of the chemical reaction. The result of thesephenomena is that the conductivity of the electrolyte is increased,thereby reducing the IR drop of the battery itself. In addition, theincrease in operating temperature of the battery also increases the opencircuit voltage of the battery.

The effect of these advantages is to provide a battery which more nearlyapproaches a characteristic curve in which the output voltage isconstant irrespective of changes in various environmental conditions, inthis case, ambient temperature.

Other objects and advantages of the present invention will be manifestfrom an examination of this description, the accompanying claims, andthe drawings.

In one embodiment of the present invention a deferred action battery isprovided, having a battery casing surrounding the electrode assembly ofthe battery, with one or more passageways or conduits disposed along thelower and upper edges of the electrodes of the cells within the battery,and terminating at each end in a port provided for ingress and egress ofelectrolyte, respectively. The passageways are defined by hoods formedintegrally with the casing.

In another aspect of the present invention, an improved method andapparatus for forming such a battery casing are provided.

Reference will now be made to the accompanying drawings in which:

FIG. 1 is a perspective view of a battery constructed in accordance withthe present invention;

FIG. 2 is a cross-sectional view taken along the section 22 of FIG. 1,illustrating the electrode assembly just subsequent to dipping in thecasing material and with the manufacturing apparatus still in place;

FIG. 3 is a top view of the battery assembly and apparatus prior todipping in the casing material;

FIG. 4 is a side view of the electrode assembly and apparatus of FIG. 3;and

FIG. 5 is a graphical illustration of the improved voltagetimecharacteristic of a battery constructed in accordance with the presentinvention.

Referring now to the drawings, there is shown a battery construction 9similar to that described and claimed in the aforementioned Jones et al.application, with a modified casing best illustrated in FIG. 1. As shownin FIGS. 2 and 3, the bat tery comprises an electrode assembly 11, whichincludes a plurality of cathodes l2, anodes l4 and partitions 16, thepartitions separating adjacent anodes l4 and cathodes 112. Thepartitions 16 are formed of impermeable, electrically conductivematerial, so that they serve to prevent electrolyte from flowing betweenthe various cells of the battery and also to electrically connect theseveral cells of the battery in series. A plurality of small insulatingspacers 18 operate to maintain a given separation between the cathode l2and anode 14 of each respective cell, and each of the cathodes 12 isprovided with a plurality of embossed or protuberant portions 20 for thepurpose of increasing electrolyte circulation in the non-reactive areasbetween the cathode and the spacer for better temperature stability andin the reactive space between anode and cathode to maintain the cellareas substantially free from undissolved salts which may be generatedduring the battery reaction. And end plate 13 is disposed in contactwith the endmost cathode 12a, and serves as an electrical connector towhich a lead may be attached.

The electrode assembly 1 1 is preferably secured together, at leasttemporarily, with a strip of insulating tape 17, shown in FIG. 4 andpartially shown in FIG. 3, which insures that the components of theelectrode assembly remain in fixed relationship, until the casing 10 isformed.

The casing 19 which surrounds the electrode assembly 11 is formed bydipping the assembly into a supply of molten casing material, which ispreferably a plastic compound, and preferably one which is relativelyrigid at room temperature but fluid at temperatures not greatly inexcess of ambient ranges. One satisfactory material which is employed iscellulose acetate butyrate. A thin inner surface film of compoundcongeals on contact with the relatively cool electrode assembly 11, andan additional thickness sets on the outer surface upon removing theassembly from the compound supply and cooling the unit.

As shown in FIG. 1, the basic body of the casing 10 also includesintegral hoods 26, 28 and 30, which are disposed over the openings inthe casing 10 communicating with edges of the electrode assembly. Eachof the hoods 26, 28 and 30' are open at both ends to form ports 32 and34 through which electrolyte may pass into or from the interior of thecasing 10. The passageways of conduits, defined by hoods 26 and 28,comprise small manifolds and extend between the ports 32 and 34. Themanifolds define openings at the edges of all of the cells of thebattery, and therefore permit some intercell leakage to occur. However,the presence of the hoods over these areas limit the cross-sectionalarea over which such leakage current may flow, which thereby maintainsthe resistance of the leakage path at a relatively high level andconsequently minimizes energy wasted by this leakage. A reinforcing stem70 for the terminal wires 72 and 74 is also formed integrally with theeasing 10 and the hoods 26, 28 and 30.

FIGS. 2, 3 and 4 illustrate portions of apparatus 35, employed forsupporting and submerging an electrode assembly 11 into the moltencasing material. The jig 35 is provided with a support bracket 51, witha centrally disposed bottom arm adapted to support the weight of theassembled battery during dipping. Two or more bottom arms 40 may beemployed, if desired. Two upper arms 42 and 44, secured to supportingmembers 41 and 43, straddle the lower arm 40 to hold the assembly inposition on the lower arm 40. Each of the arms 40, 42 and 44 extendsentirely across one side of the assembly 11, and engages an edge of eachof the electrodes thereof. The supporting members 41 and 43 for theupper arms 42 and 44 are provided with vents 46 and 48 connected throughbores and 47 to grooves 49 extending along the lower surface of each ofthe upper arms 42 and 44. The air trapped in the electrode assembly 11during dipping is permitted to expand and escape through the vents 46and 48, which remain above the level of the casing material at alltimes. Thus a uniform, smooth casing results which is free of blistersor bubbles. The

ends of the bores 45 and 47 are preferably closed by plugs 53 and 55 toprevent the casing material from entering the bores which would seal thebores and prevent the venting of air from the battery. The supportmembers 41 and 43 for the upper arms 42 and 44 are preferably adjustablymounted by a clamp (not shown) on the support bracket 51 to permit adegree of adjustability so that the jig 35 may be used on various sizesof batteries and to clamp the assemblies in place for dipping.

During dipping, the jig 35 and assembly 11 are dipped into a supply ofmolten casing material, the level of which is indicated at St) in FIG.2. The entire electrode assembly and jig assembly are therefore coatedwith casing material up to the level 50, and when the jig and theelectrode assembly are withdrawn, a coating 52 surrounds the assembly 11and that portion of the jig 35 which was submerged in the casingmaterial.

The casing material is then cut in the area 54 adjacent the lower arm40, and preferably along the line 60, and in the area 56, adjacent eachof the upper arms 42 and 44, and preferably along the line 57, wherebythe completed battery, together with its surrounding casing, may easilybe slid longitudinally off of the arms 40, 42 and 44, to free thebattery from the jig. The apertures left by the removed jig armscomprise the vent holes 34. The arms 40, 42 and 44 have taperingthicknesses to facilitate removal of the battery from the jig 35.Thereafter, the coating 52 of casing material adjacent the tip end ofthe arms 4%, 42 and 44 is preferably cut back flush with the side wallsof the casing, preferably along the lines 59, to form the ports 32 onthe other side of the battery, as illustrated in FIG. 1.

The process described above results in a battery casing in which allportions are integrally formed, including the hoods 26, 28 and 30, andthe reinforcing stem 70.

Referring now to the graph illustrated in FIG. 5, two voltage-timecharacteristic curves of a battery constructed in accordance with thepresent invention are illustrated. In both curves, the current ismaintained constant. The design maximum voltage of the battery is 7.5 v.and the design minimum is 6.25 v. The two curves differ in that thecurve 66 represents the operation of the battery with a relatively warmelectrolyte, while the curve 68 represents the operation of the batterywhen a cold electrolyte is used. In the curve 66, the voltage of thebattery rises from zero to a maximum voltage within a very short time,and then falls at a relatively constant rate until the minimum voltageof 6.25 v is reached.

In the other characteristic curve 68, which applies for a coldelectrolyte, the output voltage quickly rises above the minimum voltage,and then continues to rise over a substantial portion of the life of thebattery, and eventually becomes equal to output voltage indicated by thewarm electrolyte curve. This mode of operation contrasts sharply withthat of previously known batteries, in which the output voltage for acold electrolyte condition remains substantially below the warmelectrolyte voltage over the entire life of the battery. It is believedthat the improved characteristic is due to warming the electrolyte moreeffectively by virtue of the decreased cross-sectional area of the ports32 and 34, so that the heat generated within the battery during usecannot be dissipated as effectively. An additional advantage is that thereduction in intercell leakage improves the life and capacity of thebattery.

In the foregoing, the present invention has been sufficiently describedas to enable those skilled in the art, by applying current knowledge, toadapt the same for use under varying conditions without departing fromthe essential items of novelty involved, which are intended to bedefined and secured by the appending claims.

What is claimed is:

1. A method of forming a casing for a battery comprising the steps ofassembling a plurality of similar electrodes into a rectilinear assemblyhaving generally aligned edges and spacer means disposed betweenadjacent ones of said electrodes to define a space between the edgesthereof, disposing an elongate interference member transversely acrossthe aligned edges of said assembly and in contact therewith, submergingsaid assembly and said interference member in a body of molten casingmaterial which is substantially rigid at room temperatures whereby saidcasing material directly engages said edges, permitting said assembly toremain in said molten casing material for a predetermined period of timesufiicient to permit a layer of said material to adhere to said edgesand form a web between said edges defining said spaces, withdrawing saidelectrode assembly and said interference member with said layer of saidmaterial from said body of material, permitting said layer to solidify,and removing said interference member from said electrode assembly todefine a generally tubular manifold between said edges and said layer.

2. The method of forming a casing for a battery as defined in claim 1wherein said casing material comprises cellulose acetate butyrate.

3. The method of claim 1, wherein said interference member is agenerally horizontal cantilever member in engagement with said edgeswhich is supported at one end from an upwardly extending support, saidmethod including the step of severing said layer around said member at alocation remote from said electrode assembly 4. A method of forming acasing for a battery comprising the steps of assembling a plurality ofsimilar electrodes into a rectilinear assembly having generally alignededges and spacer means disposed between adjacent ones of said electrodesto define a space between the edges thereof, disposing an elongateinterference member transversely across the aligned edges of saidassembly and in contact therewith, submerging said assembly and saidinterference member in a body of molten casing material which issubstantially rigid at room temperatures whereby said casing materialdirectly engages said edges, permitting said assembly to remain in saidmolten casing material for a predetermined period of time suificient topermit a layer of said material to adhere to said edges and form a webbetween said edges defining said spaces, withdrawing said electrodeassembly and said interference 'member with said layer of said materialfrom said body of material, permitting said layer to solidify, removingsaid interference member from said electrode assembly to define agenerally tubular manifold between said edges and said layer, andremoving a portion of said casing material adjacent the ends of saidtubular manifold to define a port at each end of said manifold.

5. A method of forming a casing for a battery comprising the steps ofassembling a plurality of similar electrodes into a rectilinear assemblyhaving ends comprising generally aligned edges and spacer means disposedbetween adjacent ones of said electrodes to define a space between theedges thereof, disposing a plurality of elongate interference memberstransversely across the aligned edges of said assembly and in contacttherewith, said assembly being supported between said interferencemembers, submerging said assembly and said interference members in abody of molten casing material which is substantially rigid at roomtemperatures whereby said casing material directly engages said edges,permitting said assembly to remain in said molten casing material for apredetermined period of time sufficient to permit a layer of saidmaterial to adhere to said edges and form a web between said edgesdefining said spaces, withdrawing said electrode assembly and saidinterference members with said layer of said material from said body ofmaterial, permitting said layer to solidify, and removing saidinterference members from said electrode assembly to define a generallytubular manifold between said edges and said layer.

6. The method of claim 5, wherein said interference members include openchannel portions engaging said edges whereby fluid communication ismaintained between the interior of said casing and the exterior of saidbody when said assembly is submerged in said body.

1. A method of forming a casing for a battery comprising the steps ofassembling a plurality of similar electrodes into a rectilinear assemblyhaving generally aligned edges and spacer means disposed betweenadjacent ones of said electrodes to define a space between the edgesthereof, disposing an elongate interference member transversely acrossthe aligned edges of said assembly and in contact therewith, submergingsaid assembly and said interference member in a body of molten casingmaterial which is substantially rigid at room temperatures whereby saidcasing material directly engages said edges, permitting said assembly toremain in said molten casing material for a predetermined period of timesufficient to permit a layer of said material to adhere to said edgesand form a web between said edges defining said spaces, withdrawing saidelectrode assembly and said interference member with said layer of saidmaterial from said body of material, permitting said layer to solidify,and removing said interference member from said electrode assembly todefine a generally tubular manifold between said edges and said layer.2. The method of forming a casing for a battery as defined in claim 1wherein said casing material comprises cellulose acetate butyrate. 3.The method of claim 1, wherein said interference member is a generallyhorizontal cantilever member in engagement with said edges which issupported at one end from an upwardly extending support, said methodincluding the step of severing said layer around said member at alocation remote from said electrode assembly.
 4. A method of forming acasing for a battery comprising the steps of assembling a plurality ofsimilar electrodes into a rectilinear assembly having generally alignededges and spacer means disposed between adjacent ones of said electrodesto define a space between the edges thereof, disposing an elongateinterference member transversely across the aligned edges of saidassembly and in contact therewith, submerging said assembly and saidinterference member in a body of molten casing material which issubstantially rigid at room temperatures whereby said casing materialdirectLy engages said edges, permitting said assembly to remain in saidmolten casing material for a predetermined period of time sufficient topermit a layer of said material to adhere to said edges and form a webbetween said edges defining said spaces, withdrawing said electrodeassembly and said interference member with said layer of said materialfrom said body of material, permitting said layer to solidify, removingsaid interference member from said electrode assembly to define agenerally tubular manifold between said edges and said layer, andremoving a portion of said casing material adjacent the ends of saidtubular manifold to define a port at each end of said manifold.
 5. Amethod of forming a casing for a battery comprising the steps ofassembling a plurality of similar electrodes into a rectilinear assemblyhaving ends comprising generally aligned edges and spacer means disposedbetween adjacent ones of said electrodes to define a space between theedges thereof, disposing a plurality of elongate interference memberstransversely across the aligned edges of said assembly and in contacttherewith, said assembly being supported between said interferencemembers, submerging said assembly and said interference members in abody of molten casing material which is substantially rigid at roomtemperatures whereby said casing material directly engages said edges,permitting said assembly to remain in said molten casing material for apredetermined period of time sufficient to permit a layer of saidmaterial to adhere to said edges and form a web between said edgesdefining said spaces, withdrawing said electrode assembly and saidinterference members with said layer of said material from said body ofmaterial, permitting said layer to solidify, and removing saidinterference members from said electrode assembly to define a generallytubular manifold between said edges and said layer.
 6. The method ofclaim 5, wherein said interference members include open channel portionsengaging said edges whereby fluid communication is maintained betweenthe interior of said casing and the exterior of said body when saidassembly is submerged in said body.